Many consumers desire to print images such as photographs on single sheet, printable media without any margins or borders around the image. A typical problem when printing borderless images on single sheets is that image quality can be affected near the trailing edge of the printable media. A reduction in image quality near the trailing edge of the printable media can be the result of the feeding systems that ink-jet printers use to advance the media through the printer.
Specifically, ink-jet printers typically use a primary roller to advance media through the printer. The primary roller is positioned with respect to the printing portion of the printer so that the media is touched by the primary roller before the media is printed. To print a borderless image on printable media, the printable media is typically released from the primary roller and a secondary roller or feeder advances the printable media while the area adjacent the trailing edge of the media is printed. The transition between the primary roller and the secondary feeder often generates poor or reduced image quality near the trailing edge of the media because of advancing errors and changes in the position of the media with respect to the printing part of the printer. This reduction in image quality near the trialing edge of printable media is often referred to as a Bottom of Form Transition Error.
Double overdrive advancing systems have been developed to allow consumers to print borderless images on printable media. To print the trailing edge of printable media using these systems, the media is released from a pincher or nip between a driver roller and a pinch roller. Thereafter, the last part of the media is advanced using the overdrive advance system.
While relatively simple to use, such double overdrive systems have proved disadvantageous in that advance calibration parameters are often different from one advance feeding system to the other in a single printer. Typically, the advance ratio in the overdrive is higher than the advance ratio in the primary advance system for purposes of pulling the media in the print zone. Moreover, sensing of the transition point between the primary advance system and the overdrive system is not perfectly accurate, and thus the different calibration parameters are not changed at exactly the right moment. Additionally, when advanced by the primary roller, media is pressed against the print plate with a specific entry angle that enables control of the media. However, when the media is released from the pinchers of the primary advance system, the angle changes, the bending force resulting from the angle is released, and the media is pushed forward in the print zone.
Another disadvantage is that many overdrive systems do not have good traction, and thus, do not firmly feed the media at a continuous rate through the printer. This results in media advance errors near the trailing edge of the printed media. Also, if the printable media has upcurl when released from the pinchers, there is nothing in the printer that pushes the media downward. This can lead to a head crash of the pen head with the border of the media. Even if upon release from the pinchers, upcurl in the media is low, and head crash does not occur, image quality may still be affected due to the variations in the advance calibration parameters between the primary advance and overdrive systems.